test_dunders.py

"""
Tests for dunder methods from `attrib._make`.
"""

from __future__ import absolute_import, division, print_function

import copy
import pickle

import pytest

from hypothesis import given
from hypothesis.strategies import booleans

import attr

from attr._make import (
    NOTHING,
    Factory,
    _add_repr,
    _is_slot_cls,
    _make_init,
    _Nothing,
    fields,
    make_class,
)
from attr.validators import instance_of

from .utils import simple_attr, simple_class


CmpC = simple_class(cmp=True)
CmpCSlots = simple_class(cmp=True, slots=True)
ReprC = simple_class(repr=True)
ReprCSlots = simple_class(repr=True, slots=True)

# HashC is hashable by explicit definition while HashCSlots is hashable
# implicitly.  The "Cached" versions are the same, except with hash code
# caching enabled
HashC = simple_class(hash=True)
HashCSlots = simple_class(hash=None, cmp=True, frozen=True, slots=True)
HashCCached = simple_class(hash=True, cache_hash=True)
HashCSlotsCached = simple_class(
    hash=None, cmp=True, frozen=True, slots=True, cache_hash=True
)
# the cached hash code is stored slightly differently in this case
# so it needs to be tested separately
HashCFrozenNotSlotsCached = simple_class(
    frozen=True, slots=False, hash=True, cache_hash=True
)


def _add_init(cls, frozen):
    """
    Add a __init__ method to *cls*.  If *frozen* is True, make it immutable.

    This function used to be part of _make.  It wasn't used anymore however
    the tests for it are still useful to test the behavior of _make_init.
    """
    cls.__init__ = _make_init(
        cls.__attrs_attrs__,
        getattr(cls, "__attrs_post_init__", False),
        frozen,
        _is_slot_cls(cls),
        cache_hash=False,
        base_attr_map={},
        is_exc=False,
    )
    return cls


class InitC(object):
    __attrs_attrs__ = [simple_attr("a"), simple_attr("b")]


InitC = _add_init(InitC, False)


class TestAddCmp(object):
    """
    Tests for `_add_cmp`.
    """

    @given(booleans())
    def test_cmp(self, slots):
        """
        If `cmp` is False, ignore that attribute.
        """
        C = make_class(
            "C", {"a": attr.ib(cmp=False), "b": attr.ib()}, slots=slots
        )

        assert C(1, 2) == C(2, 2)

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_equal(self, cls):
        """
        Equal objects are detected as equal.
        """
        assert cls(1, 2) == cls(1, 2)
        assert not (cls(1, 2) != cls(1, 2))

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_unequal_same_class(self, cls):
        """
        Unequal objects of correct type are detected as unequal.
        """
        assert cls(1, 2) != cls(2, 1)
        assert not (cls(1, 2) == cls(2, 1))

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_unequal_different_class(self, cls):
        """
        Unequal objects of different type are detected even if their attributes
        match.
        """

        class NotCmpC(object):
            a = 1
            b = 2

        assert cls(1, 2) != NotCmpC()
        assert not (cls(1, 2) == NotCmpC())

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_lt(self, cls):
        """
        __lt__ compares objects as tuples of attribute values.
        """
        for a, b in [
            ((1, 2), (2, 1)),
            ((1, 2), (1, 3)),
            (("a", "b"), ("b", "a")),
        ]:
            assert cls(*a) < cls(*b)

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_lt_unordable(self, cls):
        """
        __lt__ returns NotImplemented if classes differ.
        """
        assert NotImplemented == (cls(1, 2).__lt__(42))

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_le(self, cls):
        """
        __le__ compares objects as tuples of attribute values.
        """
        for a, b in [
            ((1, 2), (2, 1)),
            ((1, 2), (1, 3)),
            ((1, 1), (1, 1)),
            (("a", "b"), ("b", "a")),
            (("a", "b"), ("a", "b")),
        ]:
            assert cls(*a) <= cls(*b)

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_le_unordable(self, cls):
        """
        __le__ returns NotImplemented if classes differ.
        """
        assert NotImplemented == (cls(1, 2).__le__(42))

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_gt(self, cls):
        """
        __gt__ compares objects as tuples of attribute values.
        """
        for a, b in [
            ((2, 1), (1, 2)),
            ((1, 3), (1, 2)),
            (("b", "a"), ("a", "b")),
        ]:
            assert cls(*a) > cls(*b)

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_gt_unordable(self, cls):
        """
        __gt__ returns NotImplemented if classes differ.
        """
        assert NotImplemented == (cls(1, 2).__gt__(42))

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_ge(self, cls):
        """
        __ge__ compares objects as tuples of attribute values.
        """
        for a, b in [
            ((2, 1), (1, 2)),
            ((1, 3), (1, 2)),
            ((1, 1), (1, 1)),
            (("b", "a"), ("a", "b")),
            (("a", "b"), ("a", "b")),
        ]:
            assert cls(*a) >= cls(*b)

    @pytest.mark.parametrize("cls", [CmpC, CmpCSlots])
    def test_ge_unordable(self, cls):
        """
        __ge__ returns NotImplemented if classes differ.
        """
        assert NotImplemented == (cls(1, 2).__ge__(42))


class TestAddRepr(object):
    """
    Tests for `_add_repr`.
    """

    @pytest.mark.parametrize("slots", [True, False])
    def test_repr(self, slots):
        """
        If `repr` is False, ignore that attribute.
        """
        C = make_class(
            "C", {"a": attr.ib(repr=False), "b": attr.ib()}, slots=slots
        )

        assert "C(b=2)" == repr(C(1, 2))

    @pytest.mark.parametrize("cls", [ReprC, ReprCSlots])
    def test_repr_works(self, cls):
        """
        repr returns a sensible value.
        """
        assert "C(a=1, b=2)" == repr(cls(1, 2))

    def test_infinite_recursion(self):
        """
        In the presence of a cyclic graph, repr will emit an ellipsis and not
        raise an exception.
        """

        @attr.s
        class Cycle(object):
            value = attr.ib(default=7)
            cycle = attr.ib(default=None)

        cycle = Cycle()
        cycle.cycle = cycle
        assert "Cycle(value=7, cycle=...)" == repr(cycle)

    def test_underscores(self):
        """
        repr does not strip underscores.
        """

        class C(object):
            __attrs_attrs__ = [simple_attr("_x")]

        C = _add_repr(C)
        i = C()
        i._x = 42

        assert "C(_x=42)" == repr(i)

    def test_repr_uninitialized_member(self):
        """
        repr signals unset attributes
        """
        C = make_class("C", {"a": attr.ib(init=False)})

        assert "C(a=NOTHING)" == repr(C())

    @given(add_str=booleans(), slots=booleans())
    def test_str(self, add_str, slots):
        """
        If str is True, it returns the same as repr.

        This only makes sense when subclassing a class with an poor __str__
        (like Exceptions).
        """

        @attr.s(str=add_str, slots=slots)
        class Error(Exception):
            x = attr.ib()

        e = Error(42)

        assert (str(e) == repr(e)) is add_str

    def test_str_no_repr(self):
        """
        Raises a ValueError if repr=False and str=True.
        """
        with pytest.raises(ValueError) as e:
            simple_class(repr=False, str=True)

        assert (
            "__str__ can only be generated if a __repr__ exists."
        ) == e.value.args[0]


class TestAddHash(object):
    """
    Tests for `_add_hash`.
    """

    def test_enforces_type(self):
        """
        The `hash` argument to both attrs and attrib must be None, True, or
        False.
        """
        exc_args = ("Invalid value for hash.  Must be True, False, or None.",)

        with pytest.raises(TypeError) as e:
            make_class("C", {}, hash=1),

        assert exc_args == e.value.args

        with pytest.raises(TypeError) as e:
            make_class("C", {"a": attr.ib(hash=1)}),

        assert exc_args == e.value.args

    def test_enforce_no_cache_hash_without_hash(self):
        """
        Ensure exception is thrown if caching the hash code is requested
        but attrs is not requested to generate `__hash__`.
        """
        exc_args = (
            "Invalid value for cache_hash.  To use hash caching,"
            " hashing must be either explicitly or implicitly "
            "enabled.",
        )
        with pytest.raises(TypeError) as e:
            make_class("C", {}, hash=False, cache_hash=True)
        assert exc_args == e.value.args

        # unhashable case
        with pytest.raises(TypeError) as e:
            make_class(
                "C", {}, hash=None, cmp=True, frozen=False, cache_hash=True
            )
        assert exc_args == e.value.args

    def test_enforce_no_cached_hash_without_init(self):
        """
        Ensure exception is thrown if caching the hash code is requested
        but attrs is not requested to generate `__init__`.
        """
        exc_args = (
            "Invalid value for cache_hash.  To use hash caching,"
            " init must be True.",
        )
        with pytest.raises(TypeError) as e:
            make_class("C", {}, init=False, hash=True, cache_hash=True)
        assert exc_args == e.value.args

    @given(booleans(), booleans())
    def test_hash_attribute(self, slots, cache_hash):
        """
        If `hash` is False on an attribute, ignore that attribute.
        """
        C = make_class(
            "C",
            {"a": attr.ib(hash=False), "b": attr.ib()},
            slots=slots,
            hash=True,
            cache_hash=cache_hash,
        )

        assert hash(C(1, 2)) == hash(C(2, 2))

    @given(booleans())
    def test_hash_attribute_mirrors_cmp(self, cmp):
        """
        If `hash` is None, the hash generation mirrors `cmp`.
        """
        C = make_class("C", {"a": attr.ib(cmp=cmp)}, cmp=True, frozen=True)

        if cmp:
            assert C(1) != C(2)
            assert hash(C(1)) != hash(C(2))
            assert hash(C(1)) == hash(C(1))
        else:
            assert C(1) == C(2)
            assert hash(C(1)) == hash(C(2))

    @given(booleans())
    def test_hash_mirrors_cmp(self, cmp):
        """
        If `hash` is None, the hash generation mirrors `cmp`.
        """
        C = make_class("C", {"a": attr.ib()}, cmp=cmp, frozen=True)

        i = C(1)

        assert i == i
        assert hash(i) == hash(i)

        if cmp:
            assert C(1) == C(1)
            assert hash(C(1)) == hash(C(1))
        else:
            assert C(1) != C(1)
            assert hash(C(1)) != hash(C(1))

    @pytest.mark.parametrize(
        "cls",
        [
            HashC,
            HashCSlots,
            HashCCached,
            HashCSlotsCached,
            HashCFrozenNotSlotsCached,
        ],
    )
    def test_hash_works(self, cls):
        """
        __hash__ returns different hashes for different values.
        """
        a = cls(1, 2)
        b = cls(1, 1)
        assert hash(a) != hash(b)
        # perform the test again to test the pre-cached path through
        # __hash__ for the cached-hash versions
        assert hash(a) != hash(b)

    def test_hash_default(self):
        """
        Classes are not hashable by default.
        """
        C = make_class("C", {})

        with pytest.raises(TypeError) as e:
            hash(C())

        assert e.value.args[0] in (
            "'C' objects are unhashable",  # PyPy
            "unhashable type: 'C'",  # CPython
        )

    def test_cache_hashing(self):
        """
        Ensure that hash computation if cached if and only if requested
        """

        class HashCounter:
            """
            A class for testing which counts how many times its hash
            has been requested
            """

            def __init__(self):
                self.times_hash_called = 0

            def __hash__(self):
                self.times_hash_called += 1
                return 12345

        Uncached = make_class(
            "Uncached",
            {"hash_counter": attr.ib(factory=HashCounter)},
            hash=True,
            cache_hash=False,
        )
        Cached = make_class(
            "Cached",
            {"hash_counter": attr.ib(factory=HashCounter)},
            hash=True,
            cache_hash=True,
        )

        uncached_instance = Uncached()
        cached_instance = Cached()

        hash(uncached_instance)
        hash(uncached_instance)
        hash(cached_instance)
        hash(cached_instance)

        assert 2 == uncached_instance.hash_counter.times_hash_called
        assert 1 == cached_instance.hash_counter.times_hash_called

    def test_cache_hash_serialization(self):
        """
        Tests that the hash cache is cleared on deserialization to fix
        https://github.com/python-attrs/attrs/issues/482 .
        """

        # First, check that our fix didn't break serialization without
        # hash caching.
        # We don't care about the result of this; we just want to make sure we
        # can do it without exceptions.
        hash(pickle.loads(pickle.dumps(HashCacheSerializationTestUncached)))

        def assert_hash_code_not_cached_across_serialization(original):
            # Now check our fix for #482 for when hash caching is enabled.
            original_hash = hash(original)
            round_tripped = pickle.loads(pickle.dumps(original))
            # What we want to guard against is having a stale hash code
            # when a field's hash code differs in a new interpreter after
            # deserialization.  This is tricky to test because we are,
            # of course, still running in the same interpreter.  So
            # after deserialization we reach in and change the value of
            # a field to simulate the field changing its hash code. We then
            # check that the object's hash code changes, indicating that we
            # don't have a stale hash code.
            # This could fail in two ways: (1) pickle.loads could get the hash
            # code of the deserialized value (triggering it to cache) before
            # we alter the field value.  This doesn't happen in our tested
            # Python versions.  (2) "foo" and "something different" could
            # have a hash collision on this interpreter run.   But this is
            # extremely improbable and would just result in one buggy test run.
            round_tripped.foo_string = "something different"
            assert original_hash != hash(round_tripped)

        # Slotted and dict classes implement __setstate__ differently,
        # so we need to test both cases.
        assert_hash_code_not_cached_across_serialization(
            HashCacheSerializationTestCached()
        )
        assert_hash_code_not_cached_across_serialization(
            HashCacheSerializationTestCachedSlots()
        )

    def test_caching_and_custom_setstate(self):
        """
        The combination of a custom __setstate__ and cache_hash=True is caught
        with a helpful message.

        This is needed because we handle clearing the cache after
        deserialization with a custom __setstate__. It is possible to make both
        work, but it requires some thought about how to go about it, so it has
        not yet been implemented.
        """
        with pytest.raises(
            NotImplementedError,
            match="Currently you cannot use hash caching if you "
            "specify your own __setstate__ method.",
        ):

            @attr.attrs(hash=True, cache_hash=True)
            class NoCacheHashAndCustomSetState(object):
                def __setstate__(self, state):
                    pass


# these are for use in TestAddHash.test_cache_hash_serialization
# they need to be out here so they can be un-pickled
@attr.attrs(hash=True, cache_hash=False)
class HashCacheSerializationTestUncached(object):
    foo_string = attr.ib(default="foo")


@attr.attrs(hash=True, cache_hash=True)
class HashCacheSerializationTestCached(object):
    foo_string = attr.ib(default="foo")


@attr.attrs(slots=True, hash=True, cache_hash=True)
class HashCacheSerializationTestCachedSlots(object):
    foo_string = attr.ib(default="foo")


class TestAddInit(object):
    """
    Tests for `_add_init`.
    """

    @given(booleans(), booleans())
    def test_init(self, slots, frozen):
        """
        If `init` is False, ignore that attribute.
        """
        C = make_class(
            "C",
            {"a": attr.ib(init=False), "b": attr.ib()},
            slots=slots,
            frozen=frozen,
        )
        with pytest.raises(TypeError) as e:
            C(a=1, b=2)

        assert (
            "__init__() got an unexpected keyword argument 'a'"
            == e.value.args[0]
        )

    @given(booleans(), booleans())
    def test_no_init_default(self, slots, frozen):
        """
        If `init` is False but a Factory is specified, don't allow passing that
        argument but initialize it anyway.
        """
        C = make_class(
            "C",
            {
                "_a": attr.ib(init=False, default=42),
                "_b": attr.ib(init=False, default=Factory(list)),
                "c": attr.ib(),
            },
            slots=slots,
            frozen=frozen,
        )
        with pytest.raises(TypeError):
            C(a=1, c=2)
        with pytest.raises(TypeError):
            C(b=1, c=2)

        i = C(23)
        assert (42, [], 23) == (i._a, i._b, i.c)

    @given(booleans(), booleans())
    def test_no_init_order(self, slots, frozen):
        """
        If an attribute is `init=False`, it's legal to come after a mandatory
        attribute.
        """
        make_class(
            "C",
            {"a": attr.ib(default=Factory(list)), "b": attr.ib(init=False)},
            slots=slots,
            frozen=frozen,
        )

    def test_sets_attributes(self):
        """
        The attributes are initialized using the passed keywords.
        """
        obj = InitC(a=1, b=2)
        assert 1 == obj.a
        assert 2 == obj.b

    def test_default(self):
        """
        If a default value is present, it's used as fallback.
        """

        class C(object):
            __attrs_attrs__ = [
                simple_attr(name="a", default=2),
                simple_attr(name="b", default="hallo"),
                simple_attr(name="c", default=None),
            ]

        C = _add_init(C, False)
        i = C()
        assert 2 == i.a
        assert "hallo" == i.b
        assert None is i.c

    def test_factory(self):
        """
        If a default factory is present, it's used as fallback.
        """

        class D(object):
            pass

        class C(object):
            __attrs_attrs__ = [
                simple_attr(name="a", default=Factory(list)),
                simple_attr(name="b", default=Factory(D)),
            ]

        C = _add_init(C, False)
        i = C()

        assert [] == i.a
        assert isinstance(i.b, D)

    def test_validator(self):
        """
        If a validator is passed, call it with the preliminary instance, the
        Attribute, and the argument.
        """

        class VException(Exception):
            pass

        def raiser(*args):
            raise VException(*args)

        C = make_class("C", {"a": attr.ib("a", validator=raiser)})
        with pytest.raises(VException) as e:
            C(42)

        assert (fields(C).a, 42) == e.value.args[1:]
        assert isinstance(e.value.args[0], C)

    def test_validator_slots(self):
        """
        If a validator is passed, call it with the preliminary instance, the
        Attribute, and the argument.
        """

        class VException(Exception):
            pass

        def raiser(*args):
            raise VException(*args)

        C = make_class("C", {"a": attr.ib("a", validator=raiser)}, slots=True)
        with pytest.raises(VException) as e:
            C(42)

        assert (fields(C)[0], 42) == e.value.args[1:]
        assert isinstance(e.value.args[0], C)

    @given(booleans())
    def test_validator_others(self, slots):
        """
        Does not interfere when setting non-attrs attributes.
        """
        C = make_class(
            "C", {"a": attr.ib("a", validator=instance_of(int))}, slots=slots
        )
        i = C(1)

        assert 1 == i.a

        if not slots:
            i.b = "foo"
            assert "foo" == i.b
        else:
            with pytest.raises(AttributeError):
                i.b = "foo"

    def test_underscores(self):
        """
        The argument names in `__init__` are without leading and trailing
        underscores.
        """

        class C(object):
            __attrs_attrs__ = [simple_attr("_private")]

        C = _add_init(C, False)
        i = C(private=42)
        assert 42 == i._private


class TestNothing(object):
    """
    Tests for `_Nothing`.
    """

    def test_copy(self):
        """
        __copy__ returns the same object.
        """
        n = _Nothing()
        assert n is copy.copy(n)

    def test_deepcopy(self):
        """
        __deepcopy__ returns the same object.
        """
        n = _Nothing()
        assert n is copy.deepcopy(n)

    def test_eq(self):
        """
        All instances are equal.
        """
        assert _Nothing() == _Nothing() == NOTHING
        assert not (_Nothing() != _Nothing())
        assert 1 != _Nothing()